1. Field of the Invention
This invention relates generally to surgical cutting devices, and in particular, provides a method for forming a tubular surgical cutter for use in endoscopy, arthroscopy, internal tissue resection, and other minimally-invasive surgical procedures, the method including forming the end of the cutter by folding tabs of tubal wall material.
Arthroscopic surgery techniques often involve manipulating a cutting probe through a small incision. For example, arthroscopic knee surgery often involves manually positioning the distal end of the probe against a tissue to be cut, typically against a meniscus in the knee joint. The piece of meniscus that is to be trimmed protrudes into an aperture formed in an outer tubular structure of the probe. An inner tubular structure rotates within this outer tubular structure, the inner tube including a chopping edge which sweeps by the aperture. Hence, the meniscus (or any other hard or soft tissues which protrude into the aperture) is sheared between the chopping edge of the inner tube and the edge of the aperture on the outer tubular structure.
U.S. patent application Ser. No. 08/136,426, and co-pending U.S. patent application Ser. Nos. 08/322,680, and 08/542,289 (Attorney Docket No. 16944-000130), the full disclosures of which are incorporated herein by reference, describe exemplary tissue resection devices having chopping mechanisms formed from cooperating tubular cutters. These exemplary tissue resectors include strip-cutting members which remove axial strips of tissue from an internal body cavity, the axial strips being chopped into tissue fragments by the chopping mechanism to facilitate evacuation of the tissue through the inner tube. These patent applications further describe a preferred method of use of the exemplary resection device for trans-cervical fibroid removal from the uterus and the like.
Known tubular cutters have typically been fabricated by drawing a cup of suitable material into the shape of a closed tube. This closed tube is then welded to the end of standard tubing of the appropriate size. The drawn cups are manufactured to sizes that allow the inner tubular structure to rotate smoothly inside the outer cup of the outer tubular structure, and generally provide small clearances for a good shearing action. After welding, the tube-cup assemblies are ground to create the desired opening, and also to impose the cutting edges in the tubal wall.
Although the above welded cup fabrication method has proven effective at producing tubular surgical cutters, the process does have certain drawbacks. The process requires a number of steps which must be very accurately performed to ensure cooperation between the inner and outer tubular structures. The cups must be drawn to sizes of very tight tolerance, and each must be precisely and welded to allow rotation. Achieving the required straightness in the welded structure typically requires fixturing, greatly increasing tooling costs. Furthermore, the fabrication process requires drawability, which limits the number of suitable materials and may also increase material costs.
For the above reasons, it is desirable to provide improved tubular surgical cutters and methods for their production. It would be particularly desirable if such tubular cutter production methods did not require welding of a separate cup onto the cutter tube. It would be especially beneficial if such cutter fabrication methods could be used for both the inner and outer cutter tubes, and if such fabrication methods relied on economical tube-forming procedures to provide a disposable tubular cutter assembly for use in a wide variety of minimally-invasive surgical procedures.
2. Description of the Background Art
U.S. Pat. No. 5,112,299 describes an arthroscopic surgical apparatus and method in which an elongate outer sheath member and an inner cylindrical cutting blade member are each provided with longitudinally-extending diametrically-opposed tabs having cutting edges. The tabs extend distally so that tissue positioned between the tabs is severed as the cutting blade member passes the sheath member. There is no suggestion that these tabs be folded to structurally reinforce the open ends of the cutting tubes.
U.S. Pat. No. 4,850,354 describes a surgical cutting instrument having inner and outer tubes. An opening having a corner is cut into at least one of the inner and outer tube, while the tubes themselves preferably include hemispherical ends.
U.S. Pat. No. 5,269,798, and European Patent Application Publication No. 0 499 465 A1 describe a surgical cutting instrument formed from cooperating inner and outer elongate tubular members, the distal end of each tubular member again including a hemispherical surface.
U.S. Pat. No. 4,819,635 describes a tubular microsurgery cutting apparatus having a hemispherically-ended outer tubular member in which a tubular inner sleeve reciprocates axially.
Australian Patent No. AU-B-85855/91 and German Patent No. 2848314 each describe surgical cutting instruments having rotary cutting tubes. U.S. Pat. No. 5,133,360 is generally relevant.